technologybriefs
8:33in productionCh. 1 · The Discovery/ 8:33 · ceiling 15 min
Semiconductors

Thermistor

Samuel Ruben · 1833

Faraday found it in 1833. Ruben made it usable in 1930. The rest was engineering—not insight.

The thermistor is a semiconductor resistor whose resistance changes strongly with temperature. Michael Faraday discovered its NTC behaviour in silver sulfide in 1833. Commercial production did not begin until the 1930s due to manufacturing difficulty and limited applications. Samuel Ruben invented a commercially viable version in 1930.

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Chapters & takeaways4
  1. 0:55
    The Discovery

    Michael Faraday discovered the NTC effect in silver sulfide in 1833—but it remained a lab curiosity for a century.

  2. 2:06
    The Delay

    Manufacturing difficulty and lack of clear applications delayed commercial production until the 1930s.

  3. 3:23
    The Fix

    Samuel Ruben’s 1930 invention solved reproducibility and stability—enabling real-world use.

  4. 4:58
    What Made It Work

    Commercial viability came not from new physics, but from materials control and process discipline.

Worth your time?

Yes. Study the whole thing.

4/ 5
What works
  • Delivers rapid thermal response in compact form.
  • Enables cost-effective mass production of temperature sensors.
  • Integrates directly into analogue control circuits without amplification.
What does not
  • It does not replace platinum RTDs in calibration labs.
  • It does not operate linearly without compensation.
  • It does not eliminate self-heating error in high-current applications.
Study it if
  • Design engineers building battery thermal cutoffs.
  • Technicians maintaining HVAC feedback loops.
  • Educators demonstrating semiconductor physics.
Skip it if
  • Metrologists requiring ±0.01°C stability.
  • Software teams building AI-driven climate models.
  • Policy makers assessing energy transition timelines.
The written brief1 min read

What it is and the problem it solves

A semiconductor resistor whose resistance changes strongly with temperature. It solves the problem of affordable, responsive temperature measurement in consumer and industrial electronics.

How it works

It exploits the negative temperature coefficient (NTC) of certain semiconductors: resistance drops sharply as temperature rises.

What works

Samuel Ruben’s 1930 version achieved commercial viability by overcoming earlier manufacturing difficulties—making reproducible, stable NTC devices possible for the first time.

What does not

It does not deliver stable, linear output across wide temperature ranges without calibration. Its nonlinearity and self-heating limit accuracy in high-precision metrology.

What it changes

It enables compact, fast-response, low-power thermal sensing where thermocouples or RTDs are too bulky, slow, or expensive.

Is it worth your time

Yes—if you work with precision temperature sensing, feedback control, or low-cost thermal protection in analogue circuits.

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Up next in Technology

Thermometer

· 9:54

Temperature wasn’t measured until someone decided it could be numbered — and that decision took 100 years, three failed designs, and one mercury breakthrough.

Play nextBack to Semiconductors
9:54